bike only runs on PRI

[Katlover13]

been havin a problem lately. the bike looses all power and dies (carbs are draining) when the petcock is set to either ON or RES.... it will only run now when in the PRI setting.
Does this mean my petcock is toasty? do I need to replace it? or can it just be clogged somehow and needs a good cleaning?

[The CyberPoet]

It means either:
(A) The vacuum line from the right-most carb to the petcock is not connected or is defective (not holding the vacuum), OR
(B) the petcock diaphram is bad.

I'd replace both if I were you.

Cheers,
=-= The CyberPoet

[jgalar]

I had the same problem with mine. After checking on the price of the tank valve I decided to use the auto valve as if it were a manual one (turning it to prime to run and run for off). A few days later I drove to work and realized I had not changed to prime and it worked fine on the run position.

Or in other words the internal valve can get stuck (?) and you may be able to get it unstuck by working/turning the knob.

Its not a bad idea to turn your fuel knob from time to time to prevent this happening also.

[Katlover13]

solved this problem.... I took the tank off last night and pulled the vacuum line off of the carbs. sitting in the center of the vacuum stem on the #4 carb was a small piece of rubber blocking the hole (and preventing vaccum...). It fell right out when I touched it. I have no idea what it was or where it came from. I hope that it is not a piece of the diaphram in my petcock
can that happen? can a peice of the diaphram break off and get sucked down the vacuum line?

[Black_peter]

Sure..
But that would mean that it still won't run unless it's on PRI...

[Katlover13]

Sure..
But that would mean that it still won't run unless it's on PRI...

well, then I guess I am ok since I ran the bike for 20+ min in the ON position with no problem (just idleing in the driveway with a fan on it). before, it would drain the carbs in about 2 min...
still wonder where that little peice of rubber came from and how it got there

[reconstyle]

The world may never know...

[md86]

well, then I guess I am ok since I ran the bike for 20+ min in the ON position with no problem (just idleing in the driveway with a fan on it). before, it would drain the carbs in about 2 min...

Huh , mine ran for a LONG-ass time in the driveway just with what was in the bowls . WAY more than 2 minutes for sure ....

[Black_peter]

If it ran 20 minutes without stalling, that is a good sign.
However I would put it too the test on the road. Just to make sure you are getting full flow.